Recently, a hybrid vehicle and an electric vehicle have been focused on against a backdrop of environment issues. On these vehicles, an electric motor is mounted as a motive power source, and a power storage device such as a secondary battery and a capacitor is mounted as its electric power source.
In general, according to the power storage device such as the secondary battery and the capacitor, when its temperature is decreased, its capacity is lowered and as a result, charge/discharge characteristics are lowered. Thus, according to such vehicle, when the temperature of the power storage device is lowered after a vehicle system is started, it is necessary to raise the temperature of the power storage device.
Japanese Patent Laying-Open No. 2005-332777 discloses a warm-up control device to warm up a battery by internal heat generation of the battery by controlling charge and discharge of the battery at a low temperature. This warm-up control device includes charge/discharge pattern setting means, limiter value setting means, and warm-up controlling means. The charge/discharge pattern setting means variably sets a charge/discharge pattern repeating the charge and discharge of the battery alternately in the form of a pulse, based on a state of the battery. The limiter value setting means variably sets a limiter value to limit a maximum amplitude of the charge/discharge pattern, based on a battery temperature. When the battery temperature is lower than a predetermined temperature, the warm-up controlling means executes the charge/discharge of the battery based on the charge/discharge pattern set by the charge/discharge pattern setting means, within a range of the limiter value set by the limiter value setting means.
According to this warm-up control device, the temperature rise is promoted by the internal heat generation while the battery is protected by the limiter value setting means, so that the capacity of the battery lowered when the temperature is low can be recovered promptly.
According to the above hybrid vehicle and the electric vehicle, the capacity of a power storage unit is increasingly enlarged in order to enhance acceleration performance and travel performance such as a travel duration. Means for enlarging the capacity of the power storage unit includes a constitution having the plurality of power storage devices.
However, according to the above Japanese Patent Laying-Open No. 2005-332777, temperature rise control of the power storage device in a power supply system having the plurality of power storage devices and a protection method of the power storage device at that time are not disclosed in particular.
In addition, it is necessary to raise the temperature of the power storage device promptly when the temperature of the power storage device is lowered, in order to make the best use of the merits of the enlarged capacity of the power storage device.